COMLEX-USA Pharmacology 2 — Questions and Answers
Question 1: Statins (HMG-CoA reductase inhibitors) lower LDL cholesterol primarily by:
- Increasing bile acid excretion
- Upregulating hepatic LDL receptors (Correct answer)
- Inhibiting intestinal cholesterol absorption
- Activating lipoprotein lipase
Correct answer: Upregulating hepatic LDL receptors
By inhibiting hepatic cholesterol synthesis, statins upregulate LDL receptors on hepatocytes, increasing clearance of LDL from plasma.
Question 2: Which antiepileptic drug works by blocking sodium channels and is a first-line treatment for partial and generalized tonic-clonic seizures?
- Ethosuximide
- Phenytoin (Correct answer)
- Valproic acid
- Benzodiazepines
Correct answer: Phenytoin
Phenytoin stabilizes the inactive state of voltage-gated Na+ channels, reducing neuronal excitability and preventing seizure propagation.
Question 3: The antidote for acetaminophen overdose, N-acetylcysteine (NAC), works by:
- Directly binding NAPQI
- Replenishing glutathione stores (Correct answer)
- Inhibiting CYP2E1
- Alkalinizing the urine
Correct answer: Replenishing glutathione stores
NAC serves as a glutathione precursor, replenishing hepatic glutathione stores to detoxify the toxic NAPQI metabolite of acetaminophen.
Question 4: Which receptor does naloxone antagonize to reverse opioid overdose?
- Kappa (κ) receptor only
- Delta (δ) receptor only
- Mu (μ) receptor primarily (Correct answer)
- Sigma (σ) receptor
Correct answer: Mu (μ) receptor primarily
Naloxone is a competitive antagonist primarily at mu (μ) opioid receptors, reversing respiratory depression, sedation, and miosis of opioid overdose.
Question 5: Lithium toxicity is increased by which commonly prescribed drug class due to reduced renal clearance?
- Beta-blockers
- NSAIDs (Correct answer)
- ACE inhibitors (NSAIDs both decrease lithium excretion)
- Calcium channel blockers
Correct answer: NSAIDs
NSAIDs reduce prostaglandin-mediated renal blood flow, decreasing lithium excretion and raising serum lithium levels into the toxic range.
Question 6: Which antimalarial drug causes hemolytic anemia in patients with G6PD deficiency?
- Chloroquine
- Mefloquine
- Primaquine (Correct answer)
- Atovaquone
Correct answer: Primaquine
Primaquine generates oxidative stress that overwhelms G6PD-deficient RBCs, leading to hemolysis; always screen for G6PD before prescribing.
COMLEX-USA Pharmacology 2
Statins (HMG-CoA reductase inhibitors) lower LDL cholesterol primarily by: